1. Field of the Invention
The present invention is generally directed to medical imaging. More particularly, the present invention is directed to a method and system for optimizing the radiation dose to a user and/or an operator via medical imaging equipment.
2. Background of the Invention
For medical x-ray examinations in angiography and cardiology, excellent image quality is of particular importance in order to be able to differentiate clearly between the comparatively weakly absorbing structures being examined, in particular tissue and vessels as well as any catheters and stents present, in the body of a patient. At the same time, however, care must be taken to ensure that the patient and the medical personnel are exposed to as low an x-ray dose as possible.
The quality of a medical x-ray image depends on a large number of adjustable parameters. These parameters include, on the one hand, recording parameters, i.e. parameters such as those affecting the recording conditions obtained during imaging. These include in particular the voltage and current density of the supply voltage for the x-ray radiator as well as the exposure time and the setting of an x-ray filter. The quality of an x-ray image is additionally affected by variables generally dictated by the examination conditions. These include in particular the patient's thickness, i.e. the thickness of the irradiated body tissue, the radiator/detector spacing (also known as the source-image distance, or SID for short), the density of the patient, the frame rate, the angulation of the x-ray beam, and the x-ray photon energy level.
Recently, instead of conventional radiography employing x-ray films, digital x-ray diagnostic techniques in which the recorded x-ray image is present in electronic format, i.e. in the form of digital image data, have found widespread use. This makes it possible for the x-ray image to be post-processed using electronic image processing means before it is displayed on a screen. For a digital x-ray device it is therefore necessary to adjust not only the recording parameters but also a number of image processing parameters which affect the way in which the image is post-processed by the x-ray equipment and in turn the image quality.
It is known to control the recording parameters as a function of measurable input variables, e.g. the detector input dose, in such a way that comparable image quality is achieved under different examination conditions. For an x-ray device of this kind, a parameter configuration in which characteristics of the recording parameters are stored as a function of the input variables is generally predefined. These characteristics have hitherto been determined by the manufacturer on the basis of phantom measurements or simulation calculations.
The problem here is that the image quality and radiation dose do not constitute an objectively measurable variable, but are subject to the subjective impression of the treating radiologist. The visual impression expected and experienced as optimum is largely dictated by the experience or style of an x-ray department or even by the trained knowledgeability of an individual radiologist and therefore generally differs considerably from radiologist to radiologist.
Changing the parameter configuration of an x-ray device has hitherto been performed by technical support staff, especially as the x-ray equipment user, i.e. the treating physician, generally may not have full knowledge of all the available parameters at all times. Adapting the parameter configuration to suit the individual user would therefore involve considerable cost and/or complexity, particularly as different parameter configurations would also have to be provided as part of so-called organ programs for each body organ to be recorded, each recording projection and possibly different objects to be detected (body tissue, vessels or artificial implants such as catheters or stents), and this does not therefore usually take place.
As previously discussed, the radiologist may use her personal experience to set the parameters for the medical equipment. This can result in a situation where the radiation dose is too much which is harmful to the patient and the radiologist or anyone else in the room. For example, too much radiation can result in radiation burns for the patient.
In contrast, if the radiation dose is too low, a poor image may result. This may subject the patient and the radiologist to additional radiation exposure to acquire an adequate image. The end result in both situations is that the full capability of the medical imaging equipment is not utilized and suboptimal performance is achieved.
In addition, refinements in imaging equipment have improved image quality while reducing x-ray dose rates. However, even though technological progress has reduced exposure rates, the greater exposure duration that attends more complex procedures may lead to an increased overall patient and operator exposure accompanied by a greater potential for radiation induced injury.
A need exists for a medical imaging device that provides an adequate amount of radiation dosage that limits exposure to the patient and operating personnel.
A need also exists for a medical imaging device that provides feedback that allows operating personnel to know when they are providing suboptimal parameters to the system.
A need also exists for a medical imaging device that positions the components of the medical imaging device to achieve optimal radiation exposure by maintaining diagnostic image quality.